<!DOCTYPE html PUBLIC "-//W3C//DTD XHMTL 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhmtl">
<head>
<meta http-equiv="Content-Type" content="text/html; charset="uft-8"/>
<title>节目时钟</title>
</head>
<body>
<canvas id="drawing" width="200" height="200" sytle="border:#0F0 solid 1px">program clock</canvas>
<script>
   var drawing = document.getElementById("drawing"); 
   console.log("drawing width is:"+drawing.width);
   console.log("document width is"+document.body.offsetWidth);
   console.log("document client width"+document.body.clientWidth);
</script>